Rohingya refugee sisters Nur Kaida (R) and Ruhana hug each other at their shelter at the Palongkhali refugee camp near Cox's Bazar, Bangladesh December 21, 2017. (Photo by Marko Djurica/Reuters)

The buildings of the banking district are seen through thousands of rain drops on a glass railing in central Frankfurt, Germany, Wednesday, January 11, 2017. (Photo by Michael Probst/AP Photo)

A Southwest Airlines jet takes off from Reagan National Airport with a thunderhead to the east on June 20, 2017 in Alexandria, VA. (Photo by Jonathan Newton/The Washington Post)

A 2S5 Giatsint self- propelled gun fires during tactical exercises held by artillery detachments of the Russian Eastern Military District' s 5th Army at the Sergeyevsky training ground in Primorye Territory, Russia on March 21, 2017. Over 2500 servicemen practice combat skills received in 2017 winter training exercises. (Photo by Yuri Smityuk/TASS)

Palestinians walk on a road during a power cut in Beit Lahiya in the northern Gaza Strip January 11, 2017. (Photo by Mohammed Salem/Reuters)

An angler fishes on the opening day of the salmon fishing season on the River Tay at Kenmore in Scotland, Britain January 16, 2017. (Photo by Russell Cheyne/Reuters)

A visitor feeds a food pellet to a giraffe in the Giraffe Centre in Nairobi, Kenya January 15, 2017. (Photo by Goran Tomasevic/Reuters)

A vendor drinks water as she waits for customers at a roadside flower market in Ahmedabad, India, February 8, 2017. (Photo by Amit Dave/Reuters)